fixed potential bug with deletion of implementation

ben avrahami · ben avrahami · commit 114028e62042 · 2020-10-04T20:36:08.000+03:00
diff --git a/Lib/abc.py b/Lib/abc.py
@@ -151,12 +151,13 @@ class after this function is called.
                            " subclassing")
 
     abstracts = set()
-    # Check the existing abstract methods, keep only the ones that are
-    # still abstract.
-    for name in cls.__abstractmethods__:
-        value = getattr(cls, name, None)
-        if getattr(value, "__isabstractmethod__", False):
-            abstracts.add(name)
+    # Check the existing abstract methods of the parents, keep only the ones
+    # that are not implemented.
+    for scls in cls.__bases__:
+        for name in getattr(scls, '__abstractmethods__', ()):
+            value = getattr(cls, name, None)
+            if getattr(value, "__isabstractmethod__", False):
+                abstracts.add(name)
     # Also add any other newly added abstract methods.
     for name, value in cls.__dict__.items():
         if getattr(value, "__isabstractmethod__", False):
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
@@ -516,8 +516,8 @@ def updated_foo(self):
 
             A.foo = updated_foo
             abc.update_abstractmethods(A)
-            msg = "class A with abstract methods bar, foo"
             self.assertEqual(A.__abstractmethods__, {'foo', 'bar'})
+            msg = "class A with abstract methods bar, foo"
             self.assertRaisesRegex(TypeError, msg, A)
 
         def test_update_implementation(self):
@@ -571,6 +571,26 @@ def updated_foo(self):
             A()
             self.assertFalse(hasattr(A, '__abstractmethods__'))
 
+        def test_update_del_implementation(self):
+            class A(metaclass=abc_ABCMeta):
+                @abc.abstractmethod
+                def foo(self):
+                    pass
+
+            class B(A):
+                def foo(self):
+                    pass
+
+            B()
+
+            del B.foo
+
+            abc.update_abstractmethods(B)
+
+            msg = "class B with abstract method foo"
+            self.assertRaisesRegex(TypeError, msg, B)
+
+
 
     class TestABCWithInitSubclass(unittest.TestCase):
         def test_works_with_init_subclass(self):
